Gas turbine engine compressors

ABSTRACT

In a gas turbine engine compressor, the rotor blades are carried on a drum which comprises a plurality of rotor discs axially spaced by spacer rings. The radially outer flanks of the discs define grooves between the discs into which rotor blades are inserted from inside the drum. The outer casing of the compressor can thus be made as an integral cylindrical construction welded or brayed together.

United States Patent 1191 McMurtry Apr. 30, 1974 1 lm'entorl David Rbel1$ McMul'tl'y, Bristol, 227,181 2/1960 Australia .Q. 416/215 land 776,618 6/1957 Great Britain.... 4l6/2l5 572,859 10/1945 Great Britain.... 415/217 [73] Ass'gnee' Londm" 233,643 11/1944 Switzerland 415/217 England [22] Filed: 1972 Primary Examiner-Henry F. Raduazo [21 Appl. No.: 308,583 Attorney, Agent, or Firm-Steven, Davis, Miller &

Mosher [30] Foreign Application Priority Data 7 Nov. 26, 1971 Great Britain 54935/71 ABSTRACT Cl 9 416/198, 41 /2 In a gas turbine engine compressor, the rotor blades arecarried on a drum which comprises a plurality of lllt- Cl 7 632 /99 rotor discs axially spaced by spacer rings. The radially Field Of Search outer flanks of the discs define grooves between the 415/199, 201, 216, discs into which rotor blades are inserted from inside 416/198 A the drum. The outer casing of the compressor can thus be made as an integral cylindrical construction welded [56] References Cited or brayed together.

UNITED STATES PATENTS 2,921,770 l/l960 Frankel 416/215 5 Chums 4 D'awmg F'gures GAS TURBINE ENGINE COMPRESSORS The present invention relates to axial flow compressors and relates in particular to an improved rotor drum construction and a complete compressor construction including said rotor drum.

Axial flow compressors for gas turbine engines comprise rows of rotatable and static blading, the static blading being fixed in the casing which surrounds the rotor carrying the rotatable blading. For ease of assembly the rotor, or the casing, or both, are constructed in several axial sections which are bolted togethenThe rings of bolts required for this type of assembly constitute a considerable amount of weight and are relatively expensive since they must be made of high duty material if they are not to be a limitation on the overhaul life of the engine.

The present invention provides a construction of an axial flow compressor in which the rotor discs are joined together to form a complete drum and the rotor blades are assembled on to the drum in such a manner that the rows of stator blading may be joined together to form a complete cylindrical casing without the use of bolts while still allowing for the rotor and casing to be assembled into a complete compressor.

According to the present invention a rotor drum for an axial flow compressor comprises a plurality of axially spaced apart blade supporting discs, with spacer rings therebetween, the flanks of the radially outer portions of the disc being shaped to define the walls of circumferential blade root retaining grooves in the periphery of the drum and at least one loading slot provided in the base of each groove through which blades may be passed from the inside of the drum into the respective grooves.

Also according to the present invention, a compressor for a gas turbine engine includes an outer casing comprising complete rings of stator blades axially spaced by and integrally joined to spacer rings to form an integral cylindrical structure, and a rotor drum comprising a plurality of blade supporting discs spaced apart by and connected by spacer rings, the flanks of the radially outer portions of the discs being shaped to define with the spacer rings circumferential blade retaining grooves in the periphery of the drum, and at least one loading slot provided in the base of each groove through which the blades may be passed from the inside of the drum into the respective grooves.

The phrase integrally joined should be taken to include joining by processes such as welding, brazing and diffusion bonding as opposed to joining by bolts or other releasable means.

One example of the invention will now be more particularly described with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic representation of a gas turbine engine including a compressor constructed according to the present invention,

FIG. 2 is an enlarged sectional view of a portion of the compressor of the engine of FIG. 1,

FIG. 3 is an alternative construction and illustrates a tool for inserting blades, and

FIG. 4 illustrates a filling plug and the tool for inserting it into the loading slot.

Referring now to FIG. 1, there is shown a gas turbine engine 1, having compressor means 2, combustion equipment 3, turbine means 4 and an exhaust nozzle 5 all in flow series. Part of the compressor casing is cut away to illustrate rows of rotor blades and stator blades 12.

FIG. 2 shows the compressor means in greater detail and illustrates a five stage intermediate pressure compressor having five rows of rotor blades 10 and five rows of stator blades 12'.

The rotor blades 10 are mounted in axially spaced apart rows on a rotor drum 14 which comprises six axially spaced apart rotor discs 16 connected by spacer .rings 18. The drum is connected by means of conical members 20 at each end, (only one shown), to a shaft (not shown) for driving the rotor drum 14.

The flanks of the radially outer ends of the rotor discs are shaped to define with the spacer rings, dovetail or like-shaped grooves 24 running circumferentially around the outer periphery of the rotor drum, for receiving and retaining the correspondingly shaped roots 26 of the rotor blades 10. The roots of the blades are recessed to keep the weight of the assembly to a minimum.

It will be seen that the radial centre-line of each of the discs thus becomes axially displaced from the radial centre-line of the rotor blades 10 and is disposed midway between adjacent upstream and downstream rotor blades. 1

Several beneficial results flow from this construction.

Firstly the load path from the blade root is directly into the main body of the disc, through the flanks of the disc.

Secondly, in prior art constructions where the centrelines of discs and blades are in line, a loading slot has to be cut out from the topof the disc to enable the blades to be inserted by dropping them into the loading slot from radially outside of the drum. This cut-out weakens the disc at its most highly stressed area.

With the construction of the present invention the base of the circumferential groove is formed by the spacer ring which is relatively lightly loaded in operation, and one or more cut-outs 28 can be made in the spacer ring to provide loading slots for the blades without detriment to the structure of the disc. The blades can then be inserted one at a time into the cut-out from the inside of the drum and moved circumferentially around the groove so as to be held in place in the groove. A third advantage, which flows directly from the second, is that, not only can the rotor be made as an integral drum, for example, welded or diffusion bonded together, but also the outer casing and the stator blades can be made into an integral cylindrical construction, thus eliminating any flanges and bolted joints which are used in conventional constructions, and reducing the weight of the compressor.

The integral construction of the compressor casing and stators is as follows:

The complete cylindrical casing 30 is forged and machined as a single unit. The casing comprises alternate stator blade carrying rings 32 and spacer rings 34. The stator blade carrying rings 32 are stamped with a plurality of axially extending circumferentially spaced apart slots 36 for receiving the radially outer ends of the stator blades 12, and around the outside of these rings 32 are brazed a second set of rings 38 also stamped with slots correspondingto the slots 36. The spacer rings are machined on their inner surfaces to provide recesses for receiving an abradable compound.

In an alternative construction the outer casing may be made up from a plurality of rows of stator blades axially spaced apart by, and welded to, spacer rings, and the rows of stator blades may of themselves be made up of individual blades formed with'platforms, which are welded to each other to form the ring. The spacer rings may alternatively be formed by spacer ring portions extending axially from the stator blade ring so that the assembly can be made with a single weld in between the stator blade rings.

When the machining is completed the stator blades 12 are brazed into the slots in the rings 32 so that the casing and blades become one integral cylindrical structure.

In order to assemble the compressor, the rotor drum, without the rotor blades, is located inside the casing and the blades are inserted into the grooves 24 from inside the drum through the loading slots, so as to lie in between the rows of stator blades.

When the last blade has been inserted into each groove, the loading slots are filled by means of plugs.

The rotor blades in the compressor illustrated have platforms 35 so that the narrowest part of the groove 24 must be made wide enough to allow the platforms to pass through the groove.

The stator blades 12 carry shrouds 37 at their radially inner ends and the radially outer portion'of the disc is formed with a plurality of sealing fins 39 which form a running seal with the shrouds.

Several methods are possible for filling the loading slot but the preferred method is described with reference to FIG. 3.

In the foregoing description it has been assumed that the radial depth of the discs is such that it is possible for a workman to put his hands through the centre of the discs on the inside of the drum to insert the blades.

FIG. 3 illustrates a construction in which the radial depth of the discs is such as to make such manual construction extremely difficult and use of a tool is required.

The figure shows part of the rotor drum only of a typical high pressure compressor and illustrates three stages of rotor blading 40 supported by four discs 42. As an alternative to the construction illustrated in FIG. 2 the discs each have portions 44 of a spacer ring extending axially from both flanks adjacent their rims, so that the discs can be welded, or brazed, by means of the spacer rings into a drum.

For inserting the blades one or more loading slots 46 are provided in the spacer ring between each pair of discs.

A tool is provided which consists of a rigid filling chute 47 attached to a base-plate 48. The base-plate 48 consists of three equi-angularly spaced legs which are anchored to a disc bore by means of a lug on each, and when inserted a filling chute 47 bears on the side-walls of the disc to give it support. The radially extending part of the filling chute 47 is made in two or more pieces which are hinged together and to the base-plate 48 and which are opened out and pinned in their operative positions once inserted.

Inside the chute a flexible cable can be moved to insert the blades into the filling slots. The cable has expanding jaws 50 which can be made to grip a blade root. Once a blade is inserted through the filling slot the base-plate is indexed around one blade space, and the blade released. The base-plate is then indexed back to its original position and the flexible cable retracted to pick up another blade.

Finally it is necessary to fill in the loading slot, and although there may be many ways in which this can be done, a method which can be applied to either of the compressors of FIG. 2 and FIG. 3 is shown in FIG. 4, which is a section on the line IVlV of FIG. 3.

1 A filling plug in the form of a spring plate 52 is gripped in expandable jaws 54 of a tool 56 which has arms 58 which extend outwardly from the jaws. The jaws are on the end of a flexible cable 59 which is guided to move up and down in guide rails 60 which are fitted to a base-plate (not shown) as in the tool for inserting the blades. When the jaws are pulled into the arms, the plate 52 is deformed as shown in FIG. 4. In its deformed state the plate can be inserted into the filling slot 28, and when it is released from the jaws it springs back to fill the slot.

The plate 52 has a pair of lugs 60 which engage around the root of one of the blades to prevent circumferential movement of the plate, and a land 61 between the lugs bears on the base of the blade root to prevent radial movement of the plate. Hence the plate is completely trapped.

In the above described embodiments the spacer rings in the rotor have formed the bases of the blade root retaining grooves. In an alternative construction, however, the radially outer flanks of the discs may be so shaped as to provide at least a part of the base of each groove and the spacerrings may be disposed radially inwardly of the grooves. I

We claim:

1. An axial flow compressor having a plurality of rows of rotor blades and stator blades, and a rotor drum for mounting the rotor blades, said drum comprising a plurality of axially spaced apart blade supporting discs with first spacer rings therebetween, the flanks of the radially outer portions of the discs being shaped to define the walls of circumferential blade root retaining grooves in the periphery of the drum and at least one loading slot provided in the base of each groove through which blades may be passed the inside of the drum into the respective grooves.

2. An axial flow compressor according to claim 1 and in which the first spacer rings are welded at their ends to respective adjacent rotor discs.

3. An axial flow compressor according to claim 1 and in which the first spacer rings comprise ring portions which form part of and extend axially from the rotor discs and which are welded together at points between the discs.

4. An axial flow compressor according to claim 1 and in which each first spacer ring forms the base of a respective one of the blade root retaining grooves.

5. An axial flow compressor according to claim 1 comprising an outer casing having a plurality of stator blade rings axially spaced by and integrally joined to second spacer rings to form an integral cylindrical structure, wherein the flanks of the radially outer portions of the discs are shaped to define with the first spacer rings the circumferential blade root retaining grooves in the periphery of the drum. 

1. An axial flow compressor having a plurality of rows of rotor blades and stator blades, and a rotor drum for mounting the rotor blades, said drum comprising a plurality of axially spaced apart blade supporting discs with first spacer rings therebetween, the flanks of the radially outer portions of the discs being shaped to define the walls of circumferential blade root retaining grooves in the periphery of the drum and at least one loading slot provided in the base of each groove through which blades may be passed the inside of the drum into the respective grooves.
 2. An axial flow compressor according to claim 1 and in which the first spacer rings are welded at their ends to respective adjacent rotor discs.
 3. An axial flow compressor according to claim 1 and in which the first spacer rings comprise ring portions which form part of and extend axially from the rotor discs and which are welded together at points between the discs.
 4. An axial flow compressor according to claim 1 and in which each first spacer ring forms the base of a respective one of the blade root retaining grooves.
 5. An axial flow compressor according to claim 1 comprising an outer casing having a plurality of stator blade rings axially spaced by and integrally joined to second spacer rings to form an integral cylindrical structure, wherein the flanks of the radially outer portions of the discs are shaped to define with the first spacer rings the circumferential blade root retaining grooves in the periphery of the drum. 